Stent graft device for treating abdominal aortic aneurysms

ABSTRACT

A stent graft device has an upper main tubular portion dividing into two tubular limbs and is adapted for location in an aorta having an aneurysm. The stent graft device is well suited for an aorta having a restricted section having an inner diameter smaller than the sum of the inner diameters of the iliac arteries, which branch from the aorta. The diameters of the two tubular limbs are sufficiently small to allow for both tubular limbs to be deployed side-by-side in a fully expanded state within the restricted section without being constrained by the aorta inner surface. The limbs also have distal end portions having diameters larger than the diameters of limbs at the area near the restricted section for being retained within the iliac arteries.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of percutaneous transluminaltreatment of blood vessels, aneurysms, and, particularly refers to amodular graft device for treatment of an aorta aneurysm by replacementor encasement of the affected aorta wall with the inventive graftdevice.

2. Description of the Prior Art

As it is well known in the art, an aneurysm is a widening or dilation ofa blood vessel, artery or vein, caused by thinning of the vessel wall.The rupture of the vessel wall is a lethal complication as long as itresults in massive hemorrhage. Aneurysms usually occur in arteries butmay also be seen in the heart after local damage, or in veins.

Arterial aneurysms are more common than venous and they may be caused bycongenital thinning of the muscular portions of the artery, duringatherosclerotic degeneration of the aorta or of the carotid or basilararteries, by trauma to a vessel wall, by infectious injury, or bydegeneration from other causes. The likelihood of rupture is increasedby high blood pressure.

An aneurysm in the largest artery in the human body, the aorta, willtherefore result in a very important situation. The aorta is the primaryvessel carrying blood from the heart to the rest of the circulatorysystem. The aorta arises from the base of the left ventricle of theheart and arches over and backward to the left front side of thevertebral column, or spine. Then, it passes downward along the spine anddivides into the common iliac arteries, which supply blood to theextremities.

For descriptive purposes, the aorta is usually divided into theascending aorta, the aortic arch, the thoracic descending aorta, and theabdominal aorta. The renal arteries, mesenteric arteries, and many otherbranches arise from the abdominal aorta.

The walls of the aorta are quite thick and consist primarily of strong,elastic connective tissue. The distensibility of the aorta and its majorbranches is such that this central reservoir acts as a second heartpump.

A widely used technique for treating a patient harboring an aneurysm isthe percutaneous transluminal angioplasty, generally used in thetreatment of coronary heart diseases, which technique involves thewidening of the arteries that have been dangerously narrowed under theeffects of the atherosclorosis, that is, by the buildup of depositscalled plaque on their interior walls. A flexible tube, or catheter, isfirst inserted through a skin incision into an artery. The catheter ismanipulated transluminally until it reaches the constriction site. Asmall balloon at the end of the catheter is then inflated, compressingthe plaque and widening the passage. Although this procedure has beenlargely used since the 1970s, the PTA has been generally restricted tosome vessels, coronary arteries, for example, but the use of balloonshas not been entirely successful in larger vessels like the aortabecause of, among other things, the strong calcification of the plaques.

In addition to the foregoing, with a ruptured aneurysm, a person may betreated with reduction of blood pressure and replacement of the weakenedvessel by a graft or encasement in plastic, or mechanically stoppingblood flow to or through the aneurysm.

The use of graft devices has been found successful in the treatment ofabdominal aortic aneurysms where a graft device comprising an upper mainportion and two pending limbs is inserted into the aorta with the mainportion retained in the proximal end of the aorta and respective distalends of the limbs are inserted and retained into the respective iliacarteries, thus replacing the aortic walls by the graft. However, theaortic aneurysms are very often heavily calcified and strongly narrowedby the atherosclerotic plaques. Under these circumstances, and perhapsdue to a side effect, the diameter of the iliac arteries tend to dilatewith the result that, frequently, the diameter of the aorta, in the zoneharboring the aneurysm, that is the distal aorta, is smaller than thesum of the diameters of both iliac arteries. In practice, for example,if the distal aortic diameter is 20 mm and the iliac artery diameterexceeds 11 mm, a 12 mm iliac graft device is necessary to have thedistal ends of the graft limbs inserted and retained into the respectiveiliac arteries. Thus, each graft limb must have a diameter of 12 mm, thegraft limbs being extending into and along the distal aortic aneurysm of20 mm, which, in addition, as stated above, is heavily calcified andrigid. Therefore, the graft limbs with 24 mm (12 mm+12 mm) will beconstrained under the restricted section of the aneurysm. Moreparticularly, the exceeding 4 mm in the diameter will be compressed bythe aneurysm. While the graft construction and the materials used in itsmanufacture make the graft device to be flexible enough to be locatedinto the distal aorta, through the restricted section thereof,angulation and compression of the graft limbs could be responsible forthe occurrence of limb occlusion and the resulting ischemia of thelimbs.

In view of the foregoing it would be desirable to have a graft devicecapable of being easily inserted and located into a distal aorta withaneurysm, but capable also of being accommodated in the restrictedsection without being impaired by the smaller diameter available at therestricted section of the aorta.

SUMMARY OF THE INVENTION

It is therefore one object of the present invention to provide a stentgraft device for location within an aorta having an inner diameter andits bifurcation into iliac arteries each having an inner diameter, theaorta inner diameter being smaller than a sum of the iliac innerdiameters. The graft comprises a proximal main tubular portion to beretained within an upper portion of the aorta, the proximal main tubularportion having a first diameter and being divided into two tubularlimbs, each limb having a second diameter and a distal end portion to belocated inside an associated iliac artery and to be held against aninner surface of the iliac artery. The distal end portion defines athird diameter larger than the second diameter, the second diameterbeing of an effective size such that the two tubular limbs can beaccommodated within the aorta inner diameter without restriction. Thestent graft device may be unitary, which means that the device comprisesa single-piece, non-modular construction.

It is still another object of the present invention to provide a stentgraft device of the type to be located within an aorta and itsbifurcation into iliac arteries, the graft comprising a proximal maintubular portion to be retained within an upper portion of the aorta, theproximal main tubular portion having a first diameter and dividing intotwo tubular limbs each limb having a second diameter and a distal endportion to be located inside an associated iliac artery and held againstan inner surface of the iliac artery, the distal end portion defining athird diameter larger than the second diameter, the distal end portionbeing merged with the associated graft limb through a transition flaredportion.

The above and other objects, features and advantages of this inventionwill be better understood when taken in connection with the accompanyingdrawings and description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example in the followingdrawings wherein:

FIG. 1 shows a partial cross-sectional view of an abdominal aortaaffected by an aneurysm and including a graft device of the prior art;

FIG. 2 shows a perspective elevation view of an stent graft devicedevised according to the present invention;

FIG. 3 shows a partial cross-sectional view of an abdominal Aorta,similar to FIG. 1, but treated with the graft device of FIG. 2,according to the invention;

FIG. 4 shows a side view of a distal end portion of a graft limbaccording to the invention, with a flared transition portion merging thelimb to the distal end portion; and

FIG. 5 shows a side view, similar to FIG. 4, of a distal end portionaccording to another embodiment of the invention, with a conicaltransition portion being illustrated between the limb and the distal endportion.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now referring in detail to the drawings it may be seen from FIG. 1 thatan abdominal aorta 1 comprises an upper proximal portion 2, a distalportion 3 affected by an aneurysm 4, the aorta dividing, at the lowerpart thereof, into two iliac arteries 5, with a restricted section beingformed at 6. To treat the affected patient, a known graft device 7 isinserted and retained into the aorta, the graft having a proximal maintubular portion 8 to be retained, by any known technique in the art,within upper portion 2 of the aorta. Portion 8 divides into two tubularlimbs 9, pending from portion 8 and each limb 9 ends in a distal end 10capable of being retained within the iliac arteries and against innersurfaces of these arteries.

As it is clear from the drawing, the restriction 6 constrains the twolimbs 9 of graft 7 causing a limb occlusion and ischemia of the limb. Toovercome this drawback of the prior art, the inventor has developed anew graft device as shown in FIG. 2.

According to the invention, the graft device 11, shown in FIGS. 2 and 3,has a proximal main tubular portion 12 with a first diameter D1. Portion12 divides into two tubular limbs 13, 14, pending from portion 12, eachlimb 13, 14 defining a second diameter D2 and ending in an enlargeddistal end portion 15, 16, respectively, capable of being located andfirmly retained inside an associated iliac artery 5, so as to be heldagainst an inner surface of the iliac artery. Each portion 15, 16defines a third diameter D3 at a larger, preferably cylindrical tubularwall thereof.

Diameter D1 generally is determined by the size and available section atportion 2 of aorta 1, as well as from the aneurysm size. The same occurswith diameters D2, D3, which are also determined based on the iliacsizes and aneurysm restriction. The graft, however, is manufactured in alimited plurality of sizes which must be accommodated to the aorta undertreatment, without the different diameters being capable of being variedin a graft. To facilitate accommodation of the graft inside the aortaand to avoid the constraining situation at restriction 6, diameter D2,according to the invention, is reduced as compared to the diameters usedin the prior art grafts while a new distal end portion 15, 16 is addedat the end of the limbs to define a diameter D3 which is larger thandiameter D2. Generally speaking, the shape of portion 15, 16 may becalled as having an “Elephant Foot” appearance, with the transitionbetween the limb diameter D2 to end portion diameter D3 being shaped inany generic flared configuration.

As it is shown in FIG. 4, a first embodiment shows that the transitionor merging between a limb 13 and its distal end portion 15 may bedevised through a curved trumpet-shaped transition portion 17. FIG. 5shows another embodiment where the transition portion is a conicalportion 18. In any case, distal end portion 15, 16 may be cylindrical ormay have any shape provided that the end portion is sized and configuredto be efficiently retained into the corresponding iliac artery, as shownin FIG. 3. The material from which the graft device of the invention maybe manufactured may be the same used for the graft devices of the priorart.

While preferred embodiments of the present invention have beenillustrated and described, it will be obvious to those skilled in theart that various changes and modifications may be made therein withoutdeparting from the scope of the invention as defined in the appendedclaims.

I claim:
 1. A stent graft device for deployment within an aorta having arestricted section with an inner diameter and a bifurcation into iliacarteries each having an inner diameter measured at a first location, theinner diameter of said restricted section being smaller than a sum ofthe iliac inner diameters, the graft comprising a proximal main tubularportion to be retained within an upper portion of the aorta and having afirst diameter and two tubular limbs depending from the proximal maintubular portion, each limb having a second diameter and a distal endportion for deployment inside an associated iliac artery against aninner surface of the iliac artery at the first location, the distal endportion defining a third diameter larger than the second diameter,wherein the sum of the two second diameters is less than the innerdiameter of said restricted section and each tubular limb comprises aconcave transition portion extending from the second diameter to thethird diameter.
 2. The stent graft device of claim 1, wherein thetransition portion is conical.
 3. The stent graft device of claim 2,wherein the distal end portion is cylindrical.
 4. The stent graft deviceof claim 1, wherein the second diameter is smaller than a predeterminediliac artery inner diameter and the third diameter, in an unconfinedstate, is larger than said predetermined iliac artery inner diameter. 5.The stent graft device of claim 1, wherein the stent graft device isunitary.
 6. An expandable unitary stent graft device of the type fordeployment in an aorta having a restricted section with an innerdiameter and having an inner surface bifurcation into iliac arterieseach having an inner diameter measured at a first location and an innersurface, the aorta inner diameter being smaller than the sum of theiliac inner diameters, the device comprising a proximal main tubularportion adapted for deployment within an upper portion of the aorta andhaving a first diameter and two tubular limbs depending from the maintubular portion, each limb adapted for deployment inside an associatediliac artery, each limb having a second diameter, a distal end portionhaving a third diameter larger than the second diameter and adapted tobe restricted from full expansion by the iliac artery inner surface atthe first location, and a concave transition portion extending from thesecond diameter to the third diameter, the second diameters of the twotubular limbs being sufficiently small to allow both tubular limbs to bedeployed side-by-side in a fully expanded state within the aorta innerdiameter without being constrained by the aorta inner surface.
 7. Amethod of treating an afflicted portion of an aorta, the methodcomprising the steps of: identifying an aorta having a restrictedsection with an inner diameter and having an inner surface bifurcationinto iliac arteries each having an inner diameter measured at a firstlocation and an inner surface, the aorta inner diameter being smallerthan the sum of the iliac inner diameters, implanting a stent graftdevice comprising a proximal main tubular portion having a firstdiameter and two tubular limbs depending from the main tubular portion,each limb having a second diameter and a distal end portion, the distalend portion having a third diameter larger than the second diameter and,at a location such that: (i) said main proximal portion is disposedwithin an upper portion of the aorta; (ii) each of said tubular limbs isdisposed inside an associated iliac artery; and (iii) the distal endportion is disposed within one of said iliac arteries and restrictedfrom full expansion by the iliac artery inner surface at the firstlocation, wherein the second diameters of each of said two tubular limbsare sufficiently small to allow both tubular limbs to be deployedside-by-side in a fully expanded state within the inner diameter of saidrestricted section without being constrained by the aorta inner surfaceand wherein each tubular limb comprises a concave transition portionextending from the second diameter to the third diameter.
 8. A stentgraft device for deployment within an aorta having a restricted sectionand a bifurcation into iliac arteries, the graft comprising: a proximalmain tubular portion to be retained within an upper portion of theaorta; and a first and a second tubular limb depending from saidproximal main tubular portion; wherein each of said first and secondtubular limbs comprises: (i) an elongated portion for extending acrossthe restricted section and having a first diameter; (ii) a distal endportion to be located inside an associated iliac artery and to be heldagainst an inner surface of the iliac artery, the distal end portiondefining a second diameter larger than the first diameter; and (iii) aconcave transition portion extending between said elongated portion andsaid distal end portion.